If not, it's better to switch from existing fossil fuel plants to green energy. Running a carbon scrubber on fossil fuels puts out more carbon than it saves. It's like casting heals from HP when they cost more than they heal. There might be a time for that, but it's not during combat.

Even if the scrubber itself is on green energy, if the whole grid isn't green, the energy it's using could have gone to replace fossil fuel consumption, so it's the same cost.

If you want to sequester CO2 without putting out more than you take, plant trees.

We are not on the brink of death. We may be on the brink of the point of no return (or past it depending who you ask,) but that's not immediate death. The world isn't going to die of heat in the next 10 years. There's no need to rush to something that sounds good but does more harm.